DESCRIPTION (adapted from the investigator's abstract) The pattern visual evoked potential (PVEP), obtained with checkerboard pattern reversals, is considered to be a sensitive measure of optic nerve demyelination. Latency of the P100 component of the PVEP has been reported to be abnormally prolonged in about 90 percent of patients with a clinical history of optic neuritis, despite a recovery of visual acuity and visual field in most patients. Despite its clinical utility, a multi-center PVEP trial has never been performed. The purpose of the proposed study is to develop the PVEP as a useful measure for clinical trials involving optic neuropathy. This will be achieved by demonstrating the sensitivity of the PVEP to resolved optic neuritis and by developing a protocol that can be easily instituted at multiple locations. Analysis of the uniformity of normative data collected from four institutions will assess the feasibility of using this protocol in a multi-center setting. If the results are satisfactory, a proposal to study the PVEP will be included as part of a planned optic neuritis natural history study.